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nixos/qemu-vm: Disable cache for $NIX_DISK_IMAGE

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As @domenkozar noted in #10828, cache=writeback seems to do more harm
than good:

https://github.com/NixOS/nixpkgs/issues/10828#issuecomment-164426821

He has tested it using the openstack NixOS tests and found that
cache=none significantly improves startup performance.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This commit is contained in:
aszlig 2015-12-14 17:36:22 +01:00
parent a5bc11f9eb
commit 6353f580f9
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GPG key ID: D0EBD0EC8C2DC961
1 changed files with 2 additions and 2 deletions
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4
nixos/modules/virtualisation/qemu-vm.nix
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@ -76,14 +76,14 @@ let
-virtfs local,path=$TMPDIR/xchg,security_model=none,mount_tag=xchg \
-virtfs local,path=''${SHARED_DIR:-$TMPDIR/xchg},security_model=none,mount_tag=shared \
${if cfg.useBootLoader then ''
-drive index=0,id=drive1,file=$NIX_DISK_IMAGE,if=${cfg.qemu.diskInterface},cache=writeback,werror=report \
-drive index=0,id=drive1,file=$NIX_DISK_IMAGE,if=${cfg.qemu.diskInterface},cache=none,werror=report \
-drive index=1,id=drive2,file=$TMPDIR/disk.img,media=disk \
${if cfg.useEFIBoot then ''
-pflash $TMPDIR/bios.bin \
'' else ''
''}
'' else ''
-drive index=0,id=drive1,file=$NIX_DISK_IMAGE,if=${cfg.qemu.diskInterface},cache=writeback,werror=report \
-drive index=0,id=drive1,file=$NIX_DISK_IMAGE,if=${cfg.qemu.diskInterface},cache=none,werror=report \
-kernel ${config.system.build.toplevel}/kernel \
-initrd ${config.system.build.toplevel}/initrd \
-append "$(cat ${config.system.build.toplevel}/kernel-params) init=${config.system.build.toplevel}/init regInfo=${regInfo} ${kernelConsole} $QEMU_KERNEL_PARAMS" \